BorrowChecker: opt-in + @safe annotations for node copy/preallocation

[MilesCranmerBot]

This PR integrates BorrowChecker as an opt-in safety layer (disabled by default), and annotates the core node copy/preallocation routines with BorrowChecker.@safe (plus a few @unsafe blocks where needed).

Key changes:

• Add BorrowChecker opt-in hooks (disabled by default via preferences).
• Mark allocate_container, copy_into!, leaf_copy_into!, branch_copy_into!, leaf_copy, branch_copy, and copy_node as @safe.
• Run JuliaFormatter.

Local testing (borrow checker enabled via LocalPreferences.toml):

• Julia 1.12.0: Pkg.test("DynamicExpressions")

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	master	c670472...	master / c670472...
eval/ComplexF32/evaluation	6.86 ± 0.49 ms	6.97 ± 0.52 ms	0.984 ± 0.1
eval/ComplexF64/evaluation	10.2 ± 0.76 ms	10.4 ± 1.3 ms	0.981 ± 0.14
eval/Float32/derivative	11 ± 0.77 ms	12.5 ± 1.9 ms	0.883 ± 0.15
eval/Float32/derivative_turbo	11.2 ± 0.95 ms	12.2 ± 1.9 ms	0.915 ± 0.16
eval/Float32/evaluation	2.44 ± 0.24 ms	2.48 ± 0.26 ms	0.982 ± 0.14
eval/Float32/evaluation_bumper	0.568 ± 0.016 ms	0.604 ± 0.019 ms	0.94 ± 0.039
eval/Float32/evaluation_turbo	0.503 ± 0.025 ms	0.545 ± 0.036 ms	0.924 ± 0.076
eval/Float32/evaluation_turbo_bumper	0.567 ± 0.015 ms	0.607 ± 0.021 ms	0.934 ± 0.041
eval/Float64/derivative	14 ± 0.67 ms	15.5 ± 0.85 ms	0.906 ± 0.066
eval/Float64/derivative_turbo	14 ± 0.65 ms	15.5 ± 0.78 ms	0.909 ± 0.063
eval/Float64/evaluation	2.91 ± 0.3 ms	2.94 ± 0.32 ms	0.993 ± 0.15
eval/Float64/evaluation_bumper	1.19 ± 0.041 ms	1.26 ± 0.045 ms	0.941 ± 0.047
eval/Float64/evaluation_turbo	1.02 ± 0.069 ms	1.04 ± 0.064 ms	0.98 ± 0.09
eval/Float64/evaluation_turbo_bumper	1.18 ± 0.041 ms	1.26 ± 0.046 ms	0.937 ± 0.047
utils/combine_operators/break_sharing	0.041 ± 0.0017 ms	0.0417 ± 0.002 ms	0.983 ± 0.062
utils/convert/break_sharing	27.1 ± 3.2 μs	27.7 ± 3.1 μs	0.98 ± 0.16
utils/convert/preserve_sharing	0.098 ± 0.0072 ms	0.0991 ± 0.0085 ms	0.989 ± 0.11
utils/copy/break_sharing	27.2 ± 2.7 μs	26.9 ± 2.8 μs	1.01 ± 0.15
utils/copy/preserve_sharing	0.0989 ± 0.0078 ms	0.0988 ± 0.0075 ms	1 ± 0.11
utils/count_constant_nodes/break_sharing	12.6 ± 0.77 μs	13 ± 1.4 μs	0.966 ± 0.12
utils/count_constant_nodes/preserve_sharing	0.0839 ± 0.0062 ms	0.084 ± 0.0067 ms	0.999 ± 0.11
utils/count_depth/break_sharing	13.8 ± 1 μs	13.9 ± 0.93 μs	0.992 ± 0.098
utils/count_nodes/break_sharing	12.2 ± 0.84 μs	12.6 ± 0.72 μs	0.965 ± 0.087
utils/count_nodes/preserve_sharing	0.0848 ± 0.0059 ms	0.0834 ± 0.0047 ms	1.02 ± 0.091
utils/get_set_constants!/break_sharing	0.0324 ± 0.0035 ms	0.0328 ± 0.0029 ms	0.988 ± 0.14
utils/get_set_constants!/preserve_sharing	0.172 ± 0.0093 ms	0.172 ± 0.0094 ms	0.996 ± 0.076
utils/get_set_constants_parametric	0.0462 ± 0.0051 ms	0.046 ± 0.0049 ms	1 ± 0.15
utils/has_constants/break_sharing	7.31 ± 0.69 μs	7.38 ± 0.71 μs	0.991 ± 0.13
utils/has_operators/break_sharing	2.6 ± 0.23 μs	2.6 ± 0.14 μs	1 ± 0.1
utils/hash/break_sharing	24.2 ± 1.4 μs	23.5 ± 1.2 μs	1.03 ± 0.08
utils/hash/preserve_sharing	0.099 ± 0.0061 ms	0.0993 ± 0.0071 ms	0.996 ± 0.094
utils/index_constant_nodes/break_sharing	29 ± 2.2 μs	29.8 ± 2 μs	0.974 ± 0.1
utils/index_constant_nodes/preserve_sharing	0.0991 ± 0.0066 ms	0.0992 ± 0.006 ms	0.999 ± 0.09
utils/is_constant/break_sharing	7.92 ± 0.8 μs	7.96 ± 0.73 μs	0.994 ± 0.14
utils/simplify_tree/break_sharing	30.7 ± 1.2 μs	29.3 ± 1.1 μs	1.05 ± 0.055
utils/simplify_tree/preserve_sharing	0.111 ± 0.0064 ms	0.111 ± 0.005 ms	1 ± 0.073
utils/string_tree/break_sharing	0.438 ± 0.017 ms	0.434 ± 0.018 ms	1.01 ± 0.057
utils/string_tree/preserve_sharing	0.541 ± 0.021 ms	0.531 ± 0.023 ms	1.02 ± 0.059
time_to_load	0.166 ± 0.00019 s	0.223 ± 0.0042 s	0.742 ± 0.014

Memory benchmarks

	master	c670472...	master / c670472...
eval/ComplexF32/evaluation	0.975 k allocs: 2.5 MB	0.963 k allocs: 2.46 MB	1.01
eval/ComplexF64/evaluation	0.996 k allocs: 5.07 MB	0.969 k allocs: 4.94 MB	1.03
eval/Float32/derivative	4.66 k allocs: 17.5 MB	4.64 k allocs: 17.5 MB	1
eval/Float32/derivative_turbo	4.69 k allocs: 17.7 MB	4.66 k allocs: 17.6 MB	1.01
eval/Float32/evaluation	0.966 k allocs: 1.26 MB	0.996 k allocs: 1.3 MB	0.97
eval/Float32/evaluation_bumper	0.303 k allocs: 0.393 MB	0.303 k allocs: 0.393 MB	1
eval/Float32/evaluation_turbo	0.969 k allocs: 1.26 MB	0.966 k allocs: 1.26 MB	1
eval/Float32/evaluation_turbo_bumper	0.303 k allocs: 0.393 MB	0.303 k allocs: 0.393 MB	1
eval/Float64/derivative	4.77 k allocs: 0.0349 GB	4.76 k allocs: 0.0348 GB	1
eval/Float64/derivative_turbo	4.77 k allocs: 0.0349 GB	4.77 k allocs: 0.0349 GB	0.999
eval/Float64/evaluation	0.999 k allocs: 2.56 MB	1 k allocs: 2.57 MB	0.997
eval/Float64/evaluation_bumper	0.303 k allocs: 0.771 MB	0.303 k allocs: 0.771 MB	1
eval/Float64/evaluation_turbo	0.987 k allocs: 2.53 MB	0.978 k allocs: 2.5 MB	1.01
eval/Float64/evaluation_turbo_bumper	0.303 k allocs: 0.771 MB	0.303 k allocs: 0.771 MB	1
utils/combine_operators/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/convert/break_sharing	2 k allocs: 0.123 MB	2 k allocs: 0.123 MB	1
utils/convert/preserve_sharing	2.4 k allocs: 0.192 MB	2.4 k allocs: 0.192 MB	1
utils/copy/break_sharing	2 k allocs: 0.123 MB	2 k allocs: 0.123 MB	1
utils/copy/preserve_sharing	2.4 k allocs: 0.192 MB	2.4 k allocs: 0.192 MB	1
utils/count_constant_nodes/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/count_constant_nodes/preserve_sharing	0.404 k allocs: 0.0696 MB	0.404 k allocs: 0.0696 MB	1
utils/count_depth/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/count_nodes/break_sharing	4 allocs: 0.953 kB	4 allocs: 0.953 kB	1
utils/count_nodes/preserve_sharing	0.404 k allocs: 0.0696 MB	0.404 k allocs: 0.0696 MB	1
utils/get_set_constants!/break_sharing	0.898 k allocs: 25.2 kB	0.898 k allocs: 25.2 kB	1
utils/get_set_constants!/preserve_sharing	1.7 k allocs: 0.138 MB	1.7 k allocs: 0.138 MB	1
utils/get_set_constants_parametric	1.42 k allocs: 0.0663 MB	1.42 k allocs: 0.0663 MB	1
utils/has_constants/break_sharing	4 allocs: 0.203 kB	4 allocs: 0.203 kB	1
utils/has_operators/break_sharing	4 allocs: 0.203 kB	4 allocs: 0.203 kB	1
utils/hash/break_sharing	0.104 k allocs: 2.52 kB	0.104 k allocs: 2.52 kB	1
utils/hash/preserve_sharing	0.504 k allocs: 0.0711 MB	0.504 k allocs: 0.0711 MB	1
utils/index_constant_nodes/break_sharing	2.1 k allocs: 0.094 MB	2.1 k allocs: 0.094 MB	1
utils/index_constant_nodes/preserve_sharing	2.5 k allocs: 0.163 MB	2.5 k allocs: 0.163 MB	1
utils/is_constant/break_sharing	4 allocs: 0.203 kB	4 allocs: 0.203 kB	1
utils/simplify_tree/break_sharing	0.104 k allocs: 2.52 kB	0.104 k allocs: 2.52 kB	1
utils/simplify_tree/preserve_sharing	0.504 k allocs: 0.0711 MB	0.504 k allocs: 0.0711 MB	1
utils/string_tree/break_sharing	11.9 k allocs: 0.999 MB	11.9 k allocs: 0.999 MB	1
utils/string_tree/preserve_sharing	12.3 k allocs: 1.07 MB	12.3 k allocs: 1.07 MB	1
time_to_load	0.145 k allocs: 11 kB	0.145 k allocs: 11 kB	1

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.70%. Comparing base (95541e7) to head (c670472).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
+ Coverage   96.65%   96.70%   +0.04%     
==========================================
  Files          30       30              
  Lines        2634     2639       +5     
==========================================
+ Hits         2546     2552       +6     
+ Misses         88       87       -1     

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[MilesCranmer]

This sort of thing requires more thought first, closing for now.